Upvote:1
Some airlines require you to show the credit card used for the booking at check in. This will usually be noted on your booking confirmation, but it never hurts to check the airline's website to be certain.
Upvote:4
No, you do not need anything other than the printed e-ticket and your passport (which should often be valid for at least six months beyond your travel date to satisfy immigration rules). But there are documents you may have to have. Typically, depending on your passport and destination, to enter a country you may need to apply for a visa before flying. But in any case, this is up to you to figure that, this is not the airline's job.
If you're flying domestically you can board without a passport in most places (still, some identity document may be asked), but a passport will work also.
Finally, printing the e-ticket is not completely necessary in most cases, but it is a good idea for a few reasons, such as reminding yourself of your flight times if your phone battery dies, and convincing immigration officers that you will return home by showing them your return ticket (many immigration areas do not have Wi-Fi).
Upvote:4
Since this question is about all documents that you might need, here are some that you might need. But not always.
Printed boarding pass. If your airline allows you to print your boarding pass early, do it. When flying overseas, you will have to go through a document check. But checking-in process is done at this point. I personally don't do this because I collect airliner-printed boarding passes :D
Make sure you have Visa if the country you are going to has no visa-free or VOA agreement.